1. Field of the Invention
The invention relates to a medical diagnostic method for the two-dimensional imaging of structures present in an object, which method includes the steps of
acquiring a first data set from the object in order to define voxel image values for the voxels within a three-dimensional examination zone, PA1 generating a second data set from the first data set by a filtering operation which emphasizes the structures. The invention also relates to a system for carrying out the method as well as to an associated image processing method. PA1 determining voxels which are projected onto the same pixel in a two-dimensional image, PA1 selecting at least one of these voxels in dependence on its voxel image value in the second data set, PA1 generating the two-dimensional image, the image value for the pixel then being derived from the voxel image value of the selected voxel in the first data set.
2. Description of Related Art
In this context a voxel is to be understood to mean a volume element in the three-dimensional examination zone and a pixel is an image element of the two-dimensional image. A voxel image value is a numerical value which is associated with a voxel and characterizes a physical quantity in the relevant voxel, for example the absorption of X-rays or the nuclear magnetization.
A method of this kind is already known from the publication CAR '96, Paris, pp. 260-265 (1996). The known method has a drawback in that, due to the filtering, the two-dimensional images give the observer a rather unusual image impression.
Furthermore, from the magazine "Systems and Computers in Japan", Vol. 25, No. 2, 1994, pp. 67-80, it is known to derive a two-dimensional image for medical diagnostic purposes from a three-dimensional data set by means of a so-called MIP (Maximum Intensity Projection). A MIP takes into account the largest of the image values of the voxels projected onto the same pixel in the two-dimensional image. This method does not provide suitable imaging when the examination zone contains not only the structures to be imaged but also further structures whose image values are in the same range as the image values of the structures to be imaged. In order to solve this problem, according to the known method the zones containing the desired structures are segmented by means of an automatically formed image mask. However, such automatic segmentation, where on the basis of the image values it is decided whether a voxel belongs to a part of the structure or not, can only be done inaccurately; manual segmentation, however, would be very intricate.